ABSTRACT: Institute of Medicine guidelines for weight gain in pregnancy are clear, but evidence-based treatment approaches are not widely available. This evidence gap is particularly pressing for medically vulnerable women - those who are low income and often racial/ethnic minorities. These women have the highest rates of obesity, but almost no resources to support weight control in pregnancy. Without intervention, most will exceed Institute of Medicine recommended gains and incur significant morbidity for themselves and their children. There is preliminary data from our group supporting the efficacy of digital health platforms for delivering antenatal obesity treatment among the medically vulnerable. However, our inexpensive, easily scalable approach has not been integrated and tested in real world settings, limiting broad reach and dissemination potential. Dissemination considerations are especially pressing for socioeconomically disadvantaged and minority populations because of these groups? higher obesity risk, greater potential for experiencing obesity-related comorbidities in pregnancy, and limited finances to afford alternative treatments. The Women, Infants and Children (WIC) Food and Nutrition Program is the leading public health nutrition program for pregnant women and their children in the US, and thus, it is in a unique position to meaningfully impact the obesity epidemic among the more than 9 million disadvantaged participants it serves annually. Yet no demonstrations of effective gestational weight gain interventions exist in WIC. We propose a pragmatic trial designed to rigorously test our antenatal obesity treatment approach integrated into Philadelphia WIC community clinics. We have long-standing relationships with WIC staff and prior experience conducting pragmatic clinical trials in under-resourced settings. We will randomize 438 African American and Hispanic Philadelphia County WIC participants with obesity in early pregnancy to one of two treatment arms: 1) standard WIC care; or 2) an antenatal obesity treatment arm, which includes empirically-supported behavior change goals, regular self-monitoring text messages with automated feedback, tailored skills training materials, and counseling from WIC nutritionists. Our primary outcome is prevalence of excessive gestational weight gain; we will additionally examine changes in diet and physical activity, health-related quality of life, and rates of adverse pregnancy outcomes. We will use the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) framework to evaluate the intervention?s dissemination potential and cost effectiveness in the WIC setting. The proposed project will constitute the first systematic translation of a comprehensive antenatal obesity treatment program focused on low-income, racial/ethnic minorities, using the strengths of mHealth and WIC provider counseling for intervention delivery.